Block-spiral magnetism of the low-dimensional orbital-selective Mott phase

Competing interactions can lead to novel states of matter including frustrated magnetism, an extensive field of research both from the theoretical and experimental perspectives. Here, we show that competing energy scales present in the low-dimensional orbital-selective Mott phase (OSMP) induce an exotic magnetic order, never reported before. Neutron scattering experiments on iron-based 123 ladder materials (where OSMP is relevant) already confirmed theoretical prediction of block-magnetism (magnetic order of the form ↑↑↓↓). Now we argue that another novel phase can be stabilized in multiorbital Hubbard models, i.e., ``block-spiral state''. In the latter, the magnetic islands form a spiral propagating through the chain but with the blocks maintaining their identity, namely rigidly rotating . This complex spiral state is stabilized without any apparent frustration. Phenomenological simpler models that accurately capture both electronic and spin degrees of freedom are also discussed.